1. Field of the Invention
The present invention relates to methods of interconnecting electrical circuit elements. More specifically, the present invention relates to solderless connectors for establishing and maintaining electrical contact between circuit elements. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
The conventional method of interconnecting spacially displaced electrical or electronic circuit components consists of soldering terminals on the components to conductors which deliver current to or from the components. Thus, by way of example only, electronic circuit components are often interconnected by flexible circuits. A typical flexible circuit will comprise a sheet of plastic which functions as a supporting substrate for a multiplicity of conductors. Terminal portions of these conductors will be exposed to allow for establishment of permanent electrical contact, by soldering, between the conductors of the flexible circuit and contacts on another circuit, a connector or active or passive devices. Generally speaking, it has been required that the plastic used for the substrates of prior flexible circuits be capable of withstanding the relatively high temperatures to which the plastic would be exposed during soldering.
It has been found desirable, in some applications, to replace soldering as a technique for use in establishing connections to flexible and other circuits. In these applications the requisite electrical contact may be established by mechanically pressing the terminal portions of the circuit against terminal pads on the connector, device or another circuit. Such prior art pressure connections are customarily made with the aid of a solid resilient pressure applicator, such as a rubber member, which is placed in compression to bias at least one of the components to be electrically interconnected toward the other component to hold the terminal portions thereof in electrical contact.
While pressure connections of the type briefly described above facilitate circuit assembly and repair, and also allow for the use of low cost and low temperature plastics while eliminating the time consuming and thus costly step of soldering, the prior art pressure connectors have had a serious deficiency. U.S. Pat. No. 3,825,878 is believed to exemplify prior art pressure applicators for use in connecting a flexible circuit to a printed circuit board. The pressure applicators of U.S. Pat. No. 3,825,878 are disclosed as being formed of a solid silicone rubber which is highly resilient and which has substantial memory so that it returns to its original shape. When a solid rubber member is urged in one direction, that direction being defined as the Z coordinate of the rubber, the material compresses in the Z direction. However, as a result of compression in the Z direction, the solid rubber member deforms outwardly in directions defined by coordinates X and Y which are transverse to the Z coordinate. This transverse deformation may cause relative movement between the terminal portions of the circuits and may thus result in a failure to establish the desired electrical circuit. The problem of relative terminal movement resulting from transverse deformation of the resilient pressure applicator becomes particularly acute where, as is the typical situation, it is desired to establish electrical contact between a plurality of closely spaced terminals on a pair of circuit components such as, by way of example only, terminal portions of a first flexible circuit and those of either a second flexible circuit or a printed circuit on a rigid substrate.